Ongoing Mendel Calibration

Hello,

First post as the proud owner of a mendel-parts.com complete kit! including GEN6 and reprapped parts in a fetching, white ABS from nophead. But enough of the boasting already.

In the hopes of encouraging someone with a little more experience to peruse my printouts and provide their pearls of wisdom, I'm implementing a reciprocal replies system. As I learn from experience I'll start spotting similar problems newer newbies make and post questions about on the forums. I'll endevour to contribute to forums three-fold for each of the helpful replies I receive regarding my own issues. Hopefully this will save the more experienced among us from RSI, replying to retards like me who haven't read everything out there.

My calibration is coming along reasonably well. Here are two photos in my flickr stream:

Currently waiting on the resistor kit from mendel-parts to implement a heated build platform. So yesterday I jury rigged the nichrome-ribboned heating plates from a toaster to the bottom of my aluminium build platform. I wrapped them in Kapton first of course, and still have to run the toaster in short bursts to avoid melting the kapton. The contrivance has allowed me to print multiple layers for the first time, as can be seen in the photos. With that said, I have a fair few problems still. Likely as you expect, perimeters start from the bottom right for the first layer, then top right (and top left) for subsequent layers following completion of infill on layers below. Infill starts from the bottom left. The result is relatively smooth perimeters along the bottom and left sides, and messy perimeters on top and right sides. Additionally, the solid infills look smooth for the first half of the square and then start over-filling and creating bumps and ridges for the second half of the square. Finally that long random wander the print head takes before beginning to print? All it really achieves is to allow the previously built-up pressure of melted plastic to ebb away, resulting in missing lines to begin with. Sometimes the Z axis changes during this initial random wander too, it's as if the print head is trying to enter a low earth orbit, highly irritating. The result of one random wander can be seen in the photos.

I think the rough perimeters are a knock on effect from the continued extrusion during manoeuvers at the corners. A blob builds up and fudges the smooth continuation of the next layer.

Question 1: Does anyone know good starting settings for retraction/resume speed and distance for skeinforge? I saw one suggestion on this forum, but have been unable to find it again. I would experiment but I remember being really surprised by how far the suggested retraction went.

Question 2: How might I solve the infill overflow problem? Is it really just a slower extrude rate, given that the first half looks good? Perhaps it's the messy top and right walls affecting the infill. Although I still get the problem in the earlier prints shown in the photos, when all perimeter walls look straight enough.

Question 3: How can i eliminate The random wander? I've tried various settings in Skeinforge but am unable to isolate it.


I will add my extrusion and feed rates to the thread this evening when I get home and check.
Thank you very much for reading this all,


This question is copied over at mendel-parts.com

I'm no expert but I'll try to help.
I use replicatorg with my added skeinforge 39 plugin to do my printing.
From the pictures I can see the the Flow Rate Setting is too high - mainly because the print lines are way too thick and blobby
It looks like your layer height may be too small as well as it looks 'squished' - this might only be because of the too high a flow rate.
What are the dimensions of the object you are trying to print?
Measure with the calipers at the end to see if it is right.
Have you calibrated the mendel? Editing the steps per mm in firmware?
If you could post your speed and carve settings it would be helpful.
I could upload replicatorg with the skeinforge 39 and my settings if it would of use?
Here is a good link explaining about speed settings
Also you talk of the 'wander' I would like to know how to change this also in skeinforge settings.

Helpful hints for question 1 :- I haven't really experimented with retraction but this page may be of help also this may be the thread you are talking about - very interesting...

Repeating what Nophead says..
"The restart distance should be exactly the same as the retraction otherwise you will have an excess of plastic at the start of a line. I.e. a blob. "

Helpful hints for question 2 :-

Make sure your Infill Perimeter Overlap (ratio) is correct for the material you are using...

From the skeinforge wiki..
"Infill Perimeter Overlap (ratio) : -Defines how much overlap there is between the infill pattern and perimeter loops. 0 means that the infill barely touches the perimeter, 1 gives an overlap of one complete extrusion width. A value of slightly more then 0 is recommended for a good bonding of the two. The default is 0.05. Usable values are "up to 0.7", anything larger then 0.7 can have "undesired effect". The more "springy" the filament you are using is, the higher the value you need. I for example use 0.2 for ABS and 0.7 for PP."

Helpful hints for question 3 :-
I'm not sure about this one myself - I use a raft so I don't get the problem of loosing extruder pressure before starting the main part of the print

I hope this was helpful - I'll add more to this post if I think of anything...

A couple of things I've learnt in my experience of printing on my mendel is don't rush it, don't give up and have fun. ^_^

Also you should definitely check out the tutorial section on this page

Edited 1 time(s). Last edit at 02/02/2011 11:18PM by Laurence.

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RepRap-Shop.com

Quote
Woodsmoke
Question 3: How can i eliminate The random wander? I've tried various settings in Skeinforge but am unable to isolate it.

Use the outline plugin for Skeinforge.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Fantastic! Thanks guys.

Been buried under college work lately but finally found a day to rebuild and recalibrate my Mendel. It now sports a heating element I cannibalised from a bread maker. 550 Watts odd, only takes about 40 seconds to get the build plate up to 50C haha. A good fit for it too. Photos to follow. Implementing outline.py now.

Woodsmoke
r:-9

rhmorrison Wrote:
-------------------------------------------------------
> > Question 3: How can i eliminate The random
> wander? I've tried various settings in Skeinforge
> but am unable to isolate it.
>
> Use the outline plugin for Skeinforge.

Never mind. I misunderstood what he meant by random wander. It seems to me that he may also be printing too fast and the previous layer is still soft when the following layer is being drawn.

Edited 1 time(s). Last edit at 02/14/2011 07:33PM by brnrd.

You shouldn't have any wander like that. Look at your start.gcode and see what's in there. I rewrote one that extrudes three parallel lines at the level of the first layer, then goes directly to the print. That way the print starts with full plastic in the barrel.

Aye got the same suggestion over at mendel-parts a bit back. So I dutifully applied myself to learning Gcode. Fundamental stuff, you can't really get away with picking it up as you go along. It should probably be a checkbox question next to the Captcha for thread submissions.

Can you interpret Gcode? Yes / No

It would force newbies like me to confront the obvious: It's pretty likely we'll find the answer to our own question if we look properly.

Woodsmoke
r:-9

Just a question that seems to keep popping up for me is should
Retraction distance be the same as
Restart extra distance

The wiki seems to say no but is confusing others say yes,

currently I have them different but am getting the blob build up when the extruder starts a new outer layer

If they should be the same what would be a starting recommendation?

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Experimenting in 3D in New Zealand

Here's what the documentation that came with Skeinforge says:

Quote

Restart Extra Distance
Default is zero.

Defines the restart extra distance when the thread restarts. The restart distance will be the retraction distance plus the restart extra distance.

The restart distance is set equal to the retract distance when the restart extra distance is set to 0. If it's negative, then it would be less than the retract resulting is less plastic being extruded at the beginning. This can reduce blob. If you set it positive, then you would extrude more at the beginning increasing the blob. I have it set to 0.

I'm really confused by that statement, So do I need to set both to 0 or should one be a negative and if so which one? I know I'm being a bit dim here but to me it just makes no sense.

I have set retract to 1 and restart to -1 and it seems to be better, still not perfect though, and now the first couple of layers are a bit rough. I guess I could use a raft to fix that

Edited 1 time(s). Last edit at 05/08/2011 07:38PM by NelsonRap.

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__________________________________________________________________________
Experimenting in 3D in New Zealand

Set your retract distance to 1 or some other number and leave your retract extra distance to 0. The key word here is "extra". If retract is 1 and restart extra is 0, the it would retract by 1 mm at the end of each thread and then restart by 1 mm at the start of each thread. Setting them to 1 and -1 means that there is no restart: 1-1 = 0. This would result in not enough material being extruded at the start of each thread. You'll probably see a large gap.